掺硼金刚石薄膜二次电子发射特性的研究

掺硼金刚石薄膜具有负电子亲和势和良好的电子运输性能且容易制备,作为冷阴极材料在图像显示技术和真空技术等方面都有着巨大的应用价值,引起人们的注意.从二次电子发射的机理以及影响二次电子发射系数的因素等方面,对如何利用MPCVD法制备出高二次电子发射系数的掺硼金刚石薄膜进行了综述.论述表明通过合适的工艺条件,对薄膜表面进行适当的处理,是可以制备出高二次电子发射系数的阴极用金刚石薄膜的.     

掺硼对超纳米金刚石薄膜的影响

采用微波等离子体化学气相沉积(MPCVD)技术,利用氩气、甲烷、二氧化碳混合气体,制备出平均晶粒尺寸在7.480 nm左右,表面粗糙度在15.72 nm左右的高质量的超纳米金刚石薄膜;在此工艺基础上以硼烷作为掺杂气体,合成掺硼的金刚石薄膜.表征结果显示在一定的浓度范围内随着硼烷气体的通入,金刚石薄膜的晶粒尺寸及表面粗糙度增大、结晶性变好,不再具有超纳米金刚石膜的显微结构和表面形态;同时膜材的物相组成也发生改变,金刚石组份逐渐增多,并且膜层内出现了更明显的应力以及更好的导电性能.     

硼掺杂金刚石薄膜电极在酸碱盐中的电化学性质研究

通过热丝化学气相沉积技术,在P型单晶衬底上制备了掺硼金刚石薄膜电极。采用扫描电子显微镜和X射线衍射分析了丙酮流量对硼掺杂金刚石薄膜电极的表面形貌的影响,采用循环伏安法分析硼掺杂金刚石薄膜电极在不同浓度的酸碱盐电解液中的电化学特性。结果表明,硼掺杂金刚石薄膜质量随着丙酮流量的增加而先提高后下降的趋势,并且硼掺杂金刚石薄膜电极在不同电解质中存在不同的电化学窗口,中性溶液中的电化学窗口最宽在3.2 V以上,具有极强的电化学氧化性能。     

掺硼金刚石膜的制备及其应用

金刚石虽然具有极为优异的性能,如具有很大的能隙,高的电子迁移率、空穴迁移率和高热导率,以及负的电子亲和势,但要将它用于半导体材料时还不能直接使用,必须要先进行金刚石的P型和n型掺杂。因此,研究金刚石的P型和n型掺杂具有很重要的现实意义。在金刚石薄膜中掺杂时,一般是掺入硼原子以实现P型掺杂,掺入氮原子或磷原子以实现n型掺杂。然而,由于N和P在金刚石中的施主能级太深,现在n型掺杂金刚石薄膜制备尚不成功,这是金刚石实用化的障碍。本文介绍了金刚石膜掺硼目的、方法和制备,总结了掺硼金刚石膜在微电子、电化学、光电子、工具等领域应用状况以及存在问题。     

非晶硅太阳电池窗口层材料掺硼非晶金刚石的研究

以固态掺杂方式利用过滤阴极真空电弧技术制备掺硼非晶金刚石薄膜, 获得性能优良的宽带隙p型半导体材料, 再利用等离子增强化学气相沉积技术制备p-i-n结构非晶硅太阳电池的本征层和n型层, 最终制成以掺硼非晶金刚石薄膜为窗口层的非晶硅太阳电池. 利用Lambda950紫外-可见光分光光度计表征薄膜的光学带隙, 并测试电池开路电压、短路电流、填充因子以及转化效率等参数, 再分析电池的光谱响应特性. 实验表明, 掺硼非晶金刚石薄膜的光学带隙(～2.0eV)比p型非晶硅更宽, 以掺硼非晶金刚石薄膜用作非晶硅太阳电池的窗口层, 能够改善电池的光谱响应特征, 并提高转化效率达10%以上.     

硼掺杂对直流热阴极CVD金刚石薄膜生长特性的影响

采用直流热阴极CVD法以B(OCH3)3为掺杂剂制备了硼掺杂金刚石薄膜,利用等离子体发射光谱、SEM、Raman和XRD研究了硼掺杂对金刚石薄膜生长特性的影响,通过与未掺杂金刚石薄膜的对比发现:在直流热阴极CVD系统中,低浓度硼掺杂条件下能够长时间维持稳定的辉光放电. 掺硼后辉光等离子体活性基团(Hα、Hβ、C2、CH)的种类没有改变,但C2基团的浓度升高,而CH基团的浓度下降,薄膜的生长速率提高到0.65mg·cm-2·h-1. 硼掺杂金刚石薄膜为多晶薄膜,晶体生长良好,取向以(111)晶面为主,质量较未掺杂薄膜有所提高. 硼原子以取代或填隙的方式掺杂进入金刚石晶格,没有破坏金刚石晶体结构.     

微波功率对掺氮纳米金刚石薄膜组成、结构及性能的影响

以CH4和CO2作生长金刚石薄膜的反应气体,以Ar作载气将三聚氰胺甲醇饱和溶液带入沉积室内作氮掺杂源,用微波等离子体化学气相沉积法在单晶硅衬底上制备出掺氮纳米金刚石薄膜。通过拉曼光谱、原子力显微镜、霍尔效应研究了掺氮纳米金刚石薄膜的组成、结构和导电性能,重点研究了微波输入功率对薄膜特性的影响。结果表明,制备的掺氮纳米金刚石薄膜具有良好的电子导电性,且随着激发等离子体微波功率的增大,其晶粒尺寸、晶界宽度、表面粗糙度和电导率增大,在最佳微波功率条件下制备出电子电导率高、材料质量好的纳米金刚石薄膜。     

掺硼金刚石膜的热敏特性

用微波ＰＣＶＤ法将掺硼金刚石膜淀积在Ｓｉ３Ｎ４基片上，用Ｔｉ薄膜作为欧姆接触电极蒸发在金刚石表面上，为防止Ｔｉ在高温下氧化，上面镀上了Ａｕ薄膜，从室温到６００℃范围内测试了这些金刚石膜样的电阻（Ｒ），发现Ｔ＾－１和Ｒ之间呈线性关系，若改变掺硼浓度以及热处理条件可以控制掺硼金刚石膜的热敏特性，结果表明掺硼金刚石膜显示了高的敏感性和好的稳定性，是一咱优良的热敏电阻材料。     

硼掺杂对金刚石薄膜生长特性的影响

采用HFCVD方法制备了掺硼金刚石薄膜,通过扫描电子显微镜和X射线衍射光谱对样品的表面形貌及结构进行了分析.结果表明,随着硼含量的增加,薄膜中晶粒的取向由(100)变为(111),然后趋向于无序化.硼的掺入同样影响到孪晶晶粒的形态及生长因子α,使得α变小.通过对样品的Raman光谱分析,得出在适当的硼掺杂浓度下,孪晶的出现使金刚石薄膜中的应力得到松弛,从而中心声子线Raman位移红移较小.     

掺硼金刚石/硬质合金膜基结合和摩擦磨损性能的研究

金刚石刀具涂层在碳纤维复合材料等难加工材料高效加工方面有着广阔的应用前景。在热丝化学气相沉积系统通过气体掺硼,在硬质合金表面制备了掺硼金刚石涂层。通过SEM、Raman以及压痕测试对涂层的表面形貌、成分和膜基结合性能进行了测试和分析;对涂层进行了摩擦磨损实验,研究了涂层不同环境温度下的摩擦系数及磨损率。结果表明,适量的硼掺杂可以细化金刚石晶粒,提高膜基结合力,降低摩擦系数并提高耐磨性,掺硼金刚石磨损率随温度的升高而增大,本文合适的掺硼浓度为3×10-3。     

A positron annihilation study on the defect properties of doped diamond films

Doppler broadening measurements were performed on undoped, boron doped, and sulfur doped diamond films. The defect properties in these different diamond films were analyzed and the effect of boron concentration in the B-doped diamond films on these properties was studied. The Doppler broadening measurements were characterized with the shape parameter S and the wing parameter W. From these fitted characteristic S and W values of the diamond films and plots of S vs. position implantation energy, it was deduced that undoped and S-doped diamond films are rich of vacancy-like defects, while B-doped diamond films are poor of vacancy-like defects. This difference may originate from possible different charge state of the vacancy-like defects and from the incorporation of impurities in the different growth ambient of the films. By comparing the parameters obtained in the Doppler broadening measurements of diamond films with different boron concentration, we found that S values of B-doped diamond did not decreased with the increasing of boron concentration, which suggests that more damaged regions form in the higher boron concentration samples.     

Discharge characteristics of plasma display panels with Si-doped MgO protective layers

We report on our study of the influence of varying concentrations of Si doping on the secondary electron emission (SEE) yield of MgO thin films prepared by electron beam evaporation technique. The series of Si-doped MgO films were microstructurally characterized with various tools like X-ray diffraction, scanning electron microscopy and atomic force microscopy. The optimization of the concentration of Si doping is seen to enhance the SEE yield. We discuss the correlation of SEE yield in the context of different deposition and measurement conditions and crystalline orientation.     

Structural, optical and electrical measurements on boron-doped CdO thin films

Several boron-doped CdO with different boron composition thin films have been prepared on glass substrate by a vacuum evaporation technique. The effects of boron doping on the structural, electrical and optical properties of the host CdO films were systematically studied. The X-ray diffraction study shows that some of B³⁺ ions occupied locations in interstitial positions and/or Cd²⁺-ion vacancies of CdO lattice. The band gap of B-doped CdO suffers narrowing by 30–38% compare to undoped CdO. Such band gap narrowing (BGN) was studied in the framework of the available models. Furthermore, a phenomenological evaluation of the dependence of band gap on the carrier concentration in the film samples is discussed. The electrical behaviours show that all the prepared B-doped CdO films are degenerate semiconductors. However, the boron doping influences all the optoelectrical properties of CdO. Their dc-conductivity, carrier concentration and mobility increase compare to undoped CdO film. The largest mobility of 45–47 cm²/V s was measured for 6–8% boron-doped CdO film. From near infrared transparent-conducting oxide (NIR-TCO) point of view, boron is effective for CdO donor doping.     

Ion-induced secondary electron emission from MgO and Y2O3 thin films

We report a detailed study of the electron emission from MgO and Y₂O₃ induced by the impact of 0.1-1 keV Ar⁺ ions. The mechanisms of ion-induced secondary electron emission from oxides are far less understood because charging of the target surface during ion irradiation prohibits the precise measurement of electron yield. For this study, targets were prepared by depositing 20 nm thick films of MgO and Y₂O₃ on the semi-conducting SnO₂ substrate, which helps in charge neutralization. Additionally, a pulsed ion beam was used to further reduce the surface charging. It was found that the electron yield of both targets increases with energy of the ion. However, at a given ion energy the electron yield of Y₂O₃ was larger than MgO. Another important result of this study is that the electron emission from these large band gap insulators did not show any threshold effect, in contrast to the metal targets. It may be due to local reduction of the band gap through electron promotion processes. In addition, a Monte Carlo program was used to calculate the yield of secondary electrons excited by projectile ions, recoiling target atoms and electron cascades, and average escape depth of the secondary electrons emitted from the MgO and Y₂O₃ thin films.     

Effects of doping concentration on the microstructural and optoelectrical properties of boron doped amorphous and nanocrystalline silicon films

Boron doped hydrogenated amorphous silicon thin films were prepared by plasma-enhanced chemical vapor deposition technique at various flow rate of diborane (F_B). As-deposited samples were thermally annealed at the temperature of 800 °C to obtain the doped nanocrystalline silicon (nc-Si) films. The effect of boron concentration on the microstructural, optical and electrical properties of the films was investigated. X-ray photoelectron spectroscopy (XPS) measurements demonstrated the presence of the substitutional boron in the doped films. It was found that thermal annealing can efficiently activate the dopants in films accompanying with formation of nc-Si grains. Based on the temperature-dependent conductivity measurements, it was shown that the dark conductivity of doped amorphous samples increases monotonously with the increase of doping content. While the dark conductivity of doped nc-Si films is not only determined by the concentration of dopant but also the crystallinity of the films. As increasing the flow rate of diborane, the crystallinity of doped nc-Si films decreases, which causes the decrease of dark conductivity. Finally, the high dark conductivity of 178.68 S cm⁻¹ of the B-doped nc-Si thin films can be obtained.     

CVD金刚石膜的场发射机制

利用热灯丝化学气相沉积方法在光滑的钼上沉积了金刚石膜,用扫描电子显微镜和Raman谱对金刚石膜进行了分析。结果表明金刚石膜是由许多金刚石晶粒组成,晶粒间界主要是石墨相,并且在膜内有许多缺陷。金刚石膜的场发射结果表明高浓度CH4形成的金刚石膜场发射阈位电场较低浓度CH4形成的金刚石为低。这意味着杂质（如石墨）和缺陷（悬挂键）极大地影响了膜的场发射性能。根据以上结果,提出了一种CVD金刚石膜的场发射机制即膜内的缺陷增强膜内的电场,石墨增大电子的隧穿系数以增强CVD金刚石膜的场发射。     

金刚石薄膜蓝区电致发光研究

报道了金刚石薄膜的蓝区电致发光现象,总结了几种有关金刚石薄膜蓝区发光“Ａ”带的发光机理。提出了一种提高金刚石薄膜电致发光器件发光强度的方法。     

Plasma-enhanced chemical vapor deposition of nanocrystalline diamond

Nanocrystalline diamond films have attracted considerable attention because they have a low coefficient of friction and a low electron emission threshold voltage. In this paper, the author reviews the plasma-enhanced chemical vapor deposition (PE-CVD) of nanocrystalline diamond and mainly focuses on the growth of nanocrystalline diamond by low-pressure PE-CVD. Nanocrystalline diamond particles of 200–700 nm diameter have been prepared in a 13.56 MHz low-pressure inductively coupled CH₄/CO/H₂ plasma. The bonding state of carbon atoms was investigated by ultraviolet-excited Raman spectroscopy. Electron energy loss spectroscopy identified sp²-bonded carbons around the 20–50 nm subgrains of nanocrystalline diamond particles. Plasma diagnostics using a Langmuir probe and the comparison with plasma simulation are also reviewed. The electron energy distribution functions are discussed by considering different inelastic interaction channels between electrons and heavy particles in a molecular CH₄/H₂ plasma.